Several different topics have been studied under this project: The theory of the regulation by other molecules; the assembly-disassembly of microtubules and actin filaments has been worked out; experimental and theoretical work has been done, and continues, on the perturbation of subunit exchange by the persistence of GTP at and near the ends of microtubules. Our formalism for sliding filament models of muscle contraction has been extended to include cooperative regulation by calcium. Experimental and theoretical work has been completed on the steady-state activity of the Ca-ATPase of sarcoplasmic reticulum and it has been shown that the Onsager coefficients Lij for any biochemical system are simply related to the equilibrium one-way cycle fluxes of the corresponding kinetic diagram.